Objective Only limited studies have evaluated the risk of non-selective non-steroidal anti-inflammatory drugs (nsNSAIDs) and coxibs for lower gastrointestinal (GI) adverse outcomes. The objective of this study was to evaluate risks of lower GI adverse events associated with use of celecoxib, oral and parenteral nsNSAIDs.

Design Retrospective case–crossover study.

Setting Records of all patients aged ≥20 years hospitalised for lower GI adverse events (bleeding from small or large intestine, perforation, and complicated diverticular disease) in 2006 were retrieved using ICD-9-CM diagnosis codes from inpatient claims from the Taiwan National Health Insurance database.

Interventions Case periods were defined for each patient as 1–30 days prior to hospital admission date and control period as 91–120 days prior to hospital admission date. The pharmacy prescription database was searched for NSAID use during case and control periods.

Main outcome measures We calculated adjusted self-matched ORs and 95% CIs with a conditional logistic regression model to determine the associations between NSAID use and lower GI adverse outcomes.

Results A total of 1297 patients hospitalised for lower GI adverse events were included. Celecoxib was associated with an adjusted OR of 2.33 (95% CI 0.97 to 5.59); the association became statistically significant (OR: 3.26, 95% CI 1.07 to 9.91) when a different control period (31–60 days) was applied. Both oral and parenteral nsNSAIDs significantly increased risk for lower GI adverse events (OR: 2.26, 95% CI 1.78 to 2.85 and OR: 5.64, 95% CI 3.24 to 9.82, respectively).

Conclusions Oral and parenteral NSAIDs were associated with significantly increased risk for lower GI adverse events. Celecoxib also increased risk to a comparable extent, despite risk estimates being affected slightly by the control period chosen for comparison. The association of NSAIDs with specific lower GI adverse events and long-term complications requires further investigation.